1. Technical Field
The present invention relates to a liquid crystal display device and a method of manufacturing the liquid crystal display device and, more particularly, to a liquid crystal display device that controls a liquid crystal using an electric field that is substantially horizontal with respect to a transparent substrate and a method of manufacturing the liquid crystal display device.
2. Related Art
Liquid crystal display devices that use an electric field substantially horizontal with respect to a transparent substrate, that is, liquid crystal display devices that operate in a Fringe-Field Switching (FFS) mode, an In-Plain Switching (IPS) mode, or the like, are known as the liquid crystal display devices that have high contrast and wide viewing angle.
In these liquid crystal display device, pixel electrodes, each of which is supplied with a display signal, and common electrodes that are supplied with a common electric potential both are arranged on one of transparent substrates. Each of the pixel electrodes is connected to the drain electrode of a pixel transistor formed on the one of the transparent substrates. Each of the common electrodes is connected to the lead line of a common electrode line that is formed on the one of the transparent substrate and that is supplied with a common electric potential. In addition, lower layer electrodes for external connection and upper layer electrodes laminated on the corresponding lower layer electrodes are formed at a terminal portion.
Here, the drain electrodes, the lead lines and the lower layer electrodes are initially covered with an insulating film. After that, dry etching is performed on the insulating film to thereby form openings that respectively expose a corresponding one of the drain electrodes, a corresponding one of the lead lines and a corresponding one of the lower layer electrodes. Then, the drain electrodes, the lead lines and the lower layer electrodes are respectively connected through the openings to the pixel electrodes, the common electrodes and the upper layer electrodes.
Note that JP-A-2002-296611 describes a liquid crystal display device that controls a liquid crystal using an electric field that is substantially horizontal with respect to a transparent substrate.
However, according to a method of manufacturing the above liquid crystal display device, in a process in which the drain electrode of the pixel transistor is connected to the pixel electrode, there has been a possibility that a contact resistance may increase because a residual deposit produced during dry etching intervenes between these electrodes. In addition, a residual deposit also intervenes between the lower layer electrode and upper layer electrode of the terminal portion, so that there has been a possibility that not only an increase in contact resistance but also peeling or poor connection of the upper layer electrode due to the residual deposit may occur. As a result, there has been a problem, such as poor display or delay of signal transmission.
As measures against the above problem, it is conceivable that the above residual deposit is removed by etching. However, when the residual deposit is removed by etching, another layer, which originally should not be removed, is also etched at the same time. Thus, poor formation occurs and, hence, reduces yields.